Bio Basics

I've read quite a bit in this forum but a couple of things aren't clear to me.

As far as I understand is a scaffold of PCL is used to make scaffold for a bone/organ. A resolution of 100 microns or 0.1mm is required.

My questions:
1. What happens to the PCL? Does it get absorbed into the body? Does it stay in the body replacing the bone?
2. Can we start with a more attainable resolution like 0.4mm or 400microns?
3. Is PCL being used in medical treatment or is it just an idea we all want to try?
4. Why PCL?
5. Is PCL only for bones? Can it be used to grow skin?
6. Is there a bigger site active for development of the tissue printing reprap? This forum is nice but there are only a few people here.

The acronym PCL, in this case, is polycaprolactone.
It is a polyester with a low melting point (125 degrees F) that is biodegradable and the medical form of it is biocompatable,
so it can be implanted inside the body. PCL is already in use as sutures (stitches), adhesion barriers, time release pill
coatings, and dentistry. I've heard that is being tried with some implants in animals to test to see how well it might work
in humans - but I don't know if that is true or not.

So to answer your questions:
What happens to the PCL?
It gets broken down by the body, gets reabsorbed, and exits the body (mostly in the urine stream IIRC). How long it takes
to break down depends on what is mixed with the PCL and its porosity. Essentially it can take hours to years depending on
size and porosity.

Can you start with 400 microns?
Sure you could. RepRap is open source you can do with it as you wish.
400 microns is considered to be *big* in the world of cellular research. 100 microns would be closer to what is needed.

Is PCL being used for medical treatment?
Yes. The medical version is FDA approved and there are several products on the market that use it.

Why PCL?
Its FDA approved, easy to work with, cheap (well compared to some other scaffolding materials), and cells don't die
when they come in contact with it.

Is it only for bones?
Nope, but it is a hard plastic (like tupperware) so it wouldn't make a very good skin replacement. However I have used it as a raft
to grow skin cells on and then dissolved the PCL.

Is there a bigger site for tissue printing?
Probably, but most big sites get cluttered with useless information from people that don't understand the research.
I avoid them as do most of the people that I collaborate with.

... a bone is much more than a 'static part of the body' - it's a living organ with many interactions with the surrounding body, so a 'plastik-bone' can only be a small part or a temporary fix until the body replaces the implantat with natural grown material ...

The bone replacement is gradual, but the dissolving pattern of the PCL mixture is unpredictable.
For example, if you replaced your entire femur (upper leg bone) with PCL there is no way to
predict how the PCL will dissolve. What are you going to do if it dissolves all the way through in the
middle first? Well the person is definitely going to fall over and lose muscle control for one thing...

The only direct bone replacement with PCL that I know of is for skulls. Essentially creating a PCL patch
to cover a hole in the skull (from brain surgury or trama). I don't think that procedure is FDA approved yet.

There is a approval for using PCL to mold dental crowns and root covers though. Seeing how PCL dissolves,
I'm not quite sure that I would want it in my mouth though. Ceramic crowns don't dissolve.

I think more interest with PCL and bone is to use the PCL as a scaffold to grow bone material on and then
transfer the grown bone into a human. Most likely you would want as little PCL as possible in/on the final implant,
but if you missed some of it, no big deal because it is biocompatible.

Is growing bones a big deal? To some. I personally think that growing organs is a bigger deal, but that is my
area of research so I am a bit biased. ;-)

I'm soon going to start assembling my reprap (when it arrives) and hope to use it along side my current work.

For my work I kinda use a 3D printer to directly make micron sized structures and we use PLA and other 'biodegradable' materials for this, with micron resolution. PLA is very expensive! and we're usually working with a fraction of a gram at most for our structures.
I wouldn't want to use the reprap PLA for any medical applications tbh, however I will be interested in trying to improve it's resolution. So for the time being it'll probabilly be used for printing 'examples' of the structures lol